Hofesh Shechter I approached Antony after checking that he was aware of my work, and it turned out he was – he’d seen the Choreographer’s Cut of [Shechter’s much-praised dance piece] In Your Rooms in 2009.

MM And, Antony, what was your reaction back then?

Antony Gormley I thought, this guy’s getting away with murder! No, no… All those things that I’m deeply suspicious of – rolling mists on stage, searchlights pointing at the audience – a cheap trick in anybody else’s hands, they were amazing in his. And then, there was the movement, which seemed almost to come from, well, watching Bonobo monkeys do territorial displays – something really primal. I’ve seen a fair bit of dance, and I think the way his dancers possessed the space was of a different order.

HS I’d been talking to the Barbican about doing a concert, but I thought: how can I make it more exciting? And I decided to give an artist an opportunity to have a different take on the music, rather than me just doing everything again. I wanted the concert to become more theatrical, and Antony was the person I thought of. There was the obvious connection between his work and mine: the body, and especially the idea of the single body in the cosmos.

AG He came to me with this bizarre notion that he was going to do the music and I was going to do the choreography, which I couldn’t refuse. It’s been very good fun, and also terrifying, because I’d like to think that I understand something of dance from my own work, albeit in a very different way, but actually being put in the position of having to turn a feeling into a movement… I realised very early that this was just not possible for me. Actually, during that very first session I did have these ideas that I wasn’t interested in dance per se, but in the body in space, and was thinking of how that could be posited within the matrix of Hofesh’s extraordinarily physical music. So I took bicycles, some roller skates and a wheelchair to the rehearsal space, to look at the way the body moved, not in a willed form of motion but in a momentum-created one – with a pendulum, for example.

HS But the body or bodies are not the absolute only focus of the work. There’s the world of the music, there’s the space.

AG Yes, we started with the space – that’s really important. The Barbican is amazing. You’ve got 15 metres between the front of the stage and the rear “pillars”, another seven behind them, plus a further five or more at the very back – an astonishing depth. Then there’s the fly-tower, which gives our pendulum a radius of an incredible 32 metres, and a width, once you take all the crap out, of 18-20 metres.

HS There will be a feeling that the stage is bigger than the audience, that they’re peering deep into it.

MM Is that sensation related to the title, Survivor?

HS We saw the space, talked about the spirit of the piece, and had a lot of conversations about a sense of facing the world in a helpless way that could be horrible, or beautiful.

AG Yes, that image of a singular body in space is very important, and resonates with other things I’ve done: trying to renegotiate the relationship between the subjective and personal of the one individual, and the collective or universal. I’m aware that I’m now speaking rather in tongues about our strategy, but we’ve a lot of ingredients, not least some extraordinary music.

MM On which subject, Hofesh, you’re a trained musician and always compose the music for your dance works – what can we expect this time?

HS It’s not the heavy-metal hammer-on-the-head of Political Mother! [Shechter’s last show] There are driving beats, but I’d say it’s about 50-50 between that and the more lyrical, pastoral , quiet string work. About 15 or 16 musicians in the band – roughly half – will be string players.

MM In Political Mother, the band was very much part of the action. Will it be the same here?

HS Yes, they are the show, and there’ll be 100 drummers – maybe more.

MM Antony, will there also be sculptures of yours on stage?

AG Oh yes.

HS But there will be a cast of five bodies.

MM Bodies, meaning “people”? You’ve both used that term today.

HS I think that’s the best way to define them.

AG And then, there are a few inert other bodies.

MM So, some bodies moving and some not?

AG No, the inert bodies move, because they’re capable of moving.

MM Err, right... [Shechter and Gormley laugh] You’re not making this too easy!

HS What I find interesting is that in the beginning it was easier to speak about it because it was an idea, a concept, a feeling. Now it’s becoming reality, it feels like defining it to the millimetre is to do it an injustice.

AG I’ve been pushing Hofesh hard on the idea that we shouldn’t be relying on him and his music – my excitement about this is that it is high-risk and will be being created when the audience is there, which is going to give it authenticity but also a kind of alertness, a madness. We’ll certainly go on trying to fit the pieces together beforehand, but I feel that we almost need to wait until the audience is there before we know quite what we’re dealing with: that engagement with the audience, the acknowledgement that every night will be an experiment.

HS I think it would be safe to confuse everybody with the idea that it’s definitely not a dance piece, definitely not a concert, and definitely not just an art exhibition.

MM So, how would you describe it?

HS It’s an audio-visual experience, a concert with a visual world built around and inside it.

AG There’s a large screen, too, in the middle of the stage – many of the images on that are created on stage as part of the performance. During One and Other [2009], my piece in Trafalgar Square, I got interested in surveillance, that notion of making the audience, viewer or spectator aware of the action of their own attention, and then complicating that a bit in terms of which way the camera might be facing. So it will be: who’s looking at whom?

MM Possible echoes of Pirandello there, in your desire to shake the audience out of complacency?

AG It’s important that there are two very large drums in the audience space, and that there will be elements of what happens on stage that spill out into the audience. We want to encourage the audience not to relax and be passive.

MM So, will they see themselves on screen?

AG They may well!

MM Antony, you’ve worked on major dance pieces before, such as Akram Khan and Sidi Larbi Cherkaoui’s Zero Degrees [2005] and Cherkaoui’s Sutra [2008]. How does Survivor compare?

AG This is very different. Apart from its fluidity, I’m not “doing the set”. And what’s been refreshing is the degree to which neither of us has stood on our professional high-horses. I’m not a musician, but Hofesh has been incredibly generous in giving me the feeling that everything is open for manipulation. Even though Zero Degrees was a collaboration, there was a degree to which I could only comment. Here, I’ve been given a point of contact.

HS Yes, I think it’s safe to say that I reclaimed the driving-seat with the steps, but I’m in constant and complete conversation with Antony about it, about timing, the movement itself, whether it’s what we’re looking for. It all just feels completely, constantly experimental, which is scary and exciting, and hopefully people will come in that state of mind: let’s experiment!

Survivor will be at the Barbican Theatre, London EC2, from Thurs until next Sat. Details: barbican.org.uk